1. Field of the Invention
The present invention relates to a method of increasing the content of a functional component in grain such as rice or wheat or legume such as soybean or adzuki bean, and grain or legume manufactured by the method.
2. Description of the Related Art
Recently, γ-aminobutyric acid (GABA) has attracted attention as an effective substance for maintaining health or preventing disease by suppressing an increase of blood pressure in human body. Therefore, attempts have been made to increase the content of γ-aminobutyric acid in grain such as brown rice and legume such as soybean.
For example, Japanese Patent Application Laid-Open No. 2005-52073 discloses a method of increasing the content of the γ-aminobutyric acid in brown rice by adding water to brown rice to increase the moisture content of brown rice to 20% or more, loading the brown rice increased in moisture content to a tank separately disposed, and tempering the brown rice while supplying air into the tank.
However, this method has a problem. It is necessary to add water again to brown rice, which has been once dried to a moisture content of 10% to 15%, up to a moisture content exceeding 20%. Therefore, grain must be soaked in water or water must be directly sprayed to grain. Likewise, a humidification means is required. In the processing method for brown rice by rehydration, taste of brown rice is likely to deteriorate. In addition, damage such as rice cracking may occur. Since brown rice once dried is rehydrated and thereafter dehydrated again, the manufacturing cost increases compared to general brown rice.
To prevent taste deterioration and reduce the cost required for hydration and re-dehydration of grains, it has been strongly desired to suppress the addition amount of water to grains as much as possible.
On the other hand, it is known that when the brown rice is sprouted, the content of γ-aminobutyric acid thereof significantly increases. However, it is said that the taste of brown rice with germs, which is obtained by sprouting brown rice is inferior to that of general white rice, as is described, for example, in Japanese Patent Application Laid-Open No. 2005-168444. In the circumstances, it has been desired that the amount of γ-aminobutyric acid contained in brown rice is increased more than that of general brown rice without sprouting brown rice or in such a short time that the germ portion of the brown rice is not swollen.
Another method is disclosed, for example, in Japanese Patent Application Laid-Open No. 11-151072, in which the amount of GABA contained in soybeans is increased by spraying water to the soybeans to add water thereto and stirring them in the ambient conditions of 60° C. or less.
However, this method has a problem. The pH value of spray water must be adjusted by acetic acid. In addition, the amount of spray water must be controlled so as to be a ratio of 20 to 30% by weight relative to the amount of target soybeans whose GABA content is to be increased. Besides this, soybeans must be stirred such that the sprayed water is uniformly absorbed by the soybeans.
In the circumstances, it has been desired to easily carry out a process for adding water to legume to increase the amount of GABA thereof.